Evolution Is Not Random
By Iva Fedorka
New research from the University of California, Davis, and the Max Planck Institute for Developmental Biology in Germany found that DNA mutation is not random, as previously believed.
Their results, published in 2022 in the journal Nature, challenge current thinking about evolution. Since early in the twentieth century, it was believed that mutations (and their effects) occur randomly. The researchers were looking for confirmation of that belief but found something unexpected instead.
Starting with the Genome
Three years were spent sequencing the DNA of thale cress (Arabidopsis thaliana), a flowering weed with the relatively small genome (roughly 135 million base pairs*). The specimens at the Max Planck Institute were grown in the lab to provide a controlled space for any defective plants that would be unable to survive in nature.
More than one million mutations were uncovered while processing hundreds of plants; these appeared in nonrandom patterns. Instead, patches of the genome had lower mutation rates. These sections also included more essential genes, like those related to cell growth and gene expression.
Protection from Mutations
These important regions in the genome appear to be protected from mutation. Since these areas would be more vulnerable to harm resulting from mutations, the mechanisms for DNA damage repair may also be more present.
DNA was found to be wrapped around different types of proteins in ways that predicted whether a gene was likely to mutate. This conflicts with Darwin’s theory of evolution by natural selection since it shows that the plant evolved in ways that protect its genes from mutation and therefore improve its survival.
Mutations occurred less often in functionally constrained regions of the genome: frequency is halved inside genes and reduced by more than 60 percent in essential genes. The observed mutation frequencies also accurately predict patterns of genetic polymorphisms.
Implications for the Future
Plant breeders rely on genetic variation to develop better crops and could benefit by understanding which regions of the genome tend to mutate more than others. Scientists could also better predict or develop new treatments for cancer and other diseases that result from mutations.
These discoveries produce a more complete picture of the patterns of natural variation and may lead to new theoretical and practical research on the evolutionary role of mutation.
* By comparison, the human genome has approximately 3 billion base pairs.